New wide receiver Bruce Ellington watched a pass during the workout Tuesday June 3, 2014. The San Francisco 49ers held a spring practice at their facility in Santa Clara, Calif. near the new Levi stadium.

Photo: Brant Ward, The Chronicle

New wide receiver Bruce Ellington watched a pass during the workout...

Even before Bruce Ellington could walk, his mother was struck by her baby's ability to move.

"Oh, Bruce squirmed and he squirmed a lot. It was actually hard to carry him," Gwen Ellington said, laughing. "I had to quit work and stay home because Bruce moved so much."

Over the next two decades, Bruce's coaches and teammates came to realize what Gwen already knew: The kid is in constant motion.

Before the wide receiver was selected in the fourth round by the 49ers last month, Ellington's energy - and athleticism - allowed him to cram two careers into his four years at South Carolina. He was the starting point guard on the basketball team for three seasons and played three more on the Gamecocks' football team, earning first-team all-SEC honors in 2013.

The academic all-conference pick also graduated in 3 1/2 years with a sociology degree.

"Most of us in college athletics experience athletes who give us everything they've got in one sport," said South Carolina basketball coach Frank Martin. "Bruce did that in two sports. He never ran out of enthusiasm, and he could run until the cows come home. He has unbelievable ability to sustain effort. How his body did not break down, I don't know."

How rare is it for a Division I athlete to excel in the NCAA's two highest-profile sports? South Carolina wide receivers coach Steve Spurrier Jr. got some idea when he did investigative work last year.

In 2011 and 2012, Ellington left the football team after its final regular-season game, joined the basketball team for a few weeks and returned to the gridiron when the Gamecocks began bowl-game practices. In 2011, for example, Ellington scored a game-high 17 points in a home win over Wofford, took a red-eye flight to Orlando and participated in a Capital One Bowl practice hours later.

In December, Spurrier wondered if this breakneck pre-bowl schedule was such a good idea. There were 69 other teams playing in a bowl, and he wanted to speak with coaches at other football programs. What kind of schedule did they map out for their two-sport athletes?

The problem: Ellington was in a class by himself.

"I couldn't find another team - I couldn't find another player in the country that also played basketball that was about to play in a bowl game," Spurrier said. "So we just let him go."

Ellington, who scored 17 points in three basketball games before returning to football, didn't get exhausted by his two-sport demands: In a tribute to his tirelessness, he had six catches for 140 yards and two touchdowns and also threw a 9-yard scoring pass in a 34-24 win over Wisconsin in the Capital One Bowl.

After that Jan. 1 game, Ellington left the basketball team to focus on training for the NFL draft, meaning his performance capped a rare college career that included 1,586 receiving yards, 993 return yards, 148 rushing yards, 17 touchdowns, 893 points, 238 assists and 218 rebounds.

Not included in those stats: The number of times Ellington, 5-foot-9 and 197 pounds, waved off coaches suggesting he slow down.

In the sweltering Columbia, S.C., summers, Ellington routinely performed his personal two-a-days: He attended back-to-back running and weight-lifting sessions with the football and basketball teams. His only break came when he drove to the gym.

Niners running back Marcus Lattimore, his teammate at South Carolina, was amazed by Ellington's double duty. Spurrier was also wowed - and worried: "I'd be like, 'Bruce, what are you doing?' But he'd always say, 'I'm fine. Don't worry about me.' What could you do? He never showed signs of fatigue, weakness or injury."

Ellington, who ran track and played football, basketball and baseball as a senior at Berkeley High in Moncks Corner, S.C., never worried his body would betray him. And his confidence came from knowing what it had allowed him to do in the past.

He was rated the No. 12 high school point guard in the country by Scout.com and was a finalist for Mr. Football in the state as a senior when, as a quarterback, he led the team to a state championship by collecting 2,878 all-purpose yards and accounting for 29 touchdowns.

In the gym, he used his 39-inch vertical jump to do 360-degree dunks. In the weight room, he squatted 600 pounds as a 180-pound junior.

"I felt like I knew what my body could handle in college," Ellington said. "It's my body, so I'm good. I'm not feeling aches and pains. I didn't really listen to what other people said. It's not their body, so I just went after it. I really think it's a mind thing. I think if you say, 'Man, I'm tired. My legs hurt,' that's not good. So I always just said, 'I don't get tired.' "

His stamina was on display in the 2009 state championship football game, when Berkeley entered the fourth quarter trailing by 10 points. In response, Ellington, who ran a 4.45-second 40-yard dash at this year's NFL combine, did what he's always done best: run. He finished with 191 rushing yards and four touchdowns.

"In the fourth quarter we ran two plays, and they were both basically about giving Bruce the ball: triple option and quarterback counter," former Berkeley coach Jerry Brown said. "We won by nine points. ... I probably should have done that earlier."

Brown, a 43-year coaching veteran who has mentored seven other NFL players, a list that includes Ellington's cousin, Cardinals running back Andre Ellington, counts his former quarterback as the "most dominating" high school football player he's seen.

However, despite his football prowess - and 5-foot-9 stature - Ellington arrived at South Carolina determined to pave a path to the NBA. As a freshman, he didn't play football. Instead, he led the Gamecocks' basketball team in scoring and was named to the SEC All-Freshman team.

Spurrier had unsuccessfully recruited Ellington in high school, but it was Lattimore who eventually wooed him to the football team in 2011.

Three years later, Lattimore, an in-state high school legend who had beaten out Ellington for Mr. Football honors, is eager to see what his friend can accomplish when finally focused on one sport. Ellington, who was also a running back in high school, has played only wide receiver for three seasons.

However, his mom would offer he's been playing the position since childhood when he often spent hours alone throwing a football from one end of the backyard to the other.

"He tried to beat the football to the other side," Gwen Ellington said.

Could he do it?

"Oh yeah, he could always run and catch it," she said. "He's always wanted to just run and run and run. Once he found out he can run, he's just never stopped."